Migrate existing NFS PVCs to Longhorn

1. Create myapp-target pvc manifest. Set StorageClass to longhorn.

2. Make sure our myapp-source pvc is not in use: k scale deploy -n example myapp --replicas=0

3. Use the volume migration job: k apply -f data_migration.yaml namespace=example, source=myapp-pvc, target=myapp-target

4. Check if job is complete: k describe job volume-migration -n example

5. Delete job once it is no longer needed: k delete job volume-migration -n example

6. Test new pvc: k scale deploy -n example myapp --replicas=1

7. If everything is good, clean up old pvc: k delete pvc -n example myapp-source